The invention relates to flexible circuits that are useful in suspension arm assemblies, for example, in disc drive units.
Flexible circuits can be useful for a variety of applications for connecting elements that can move relative to each other. For example, a transducer can be mounted on a moveable arm or the like such that the transducer can perform measurements at different location. The moveable arm generally includes a suspension assembly that provides for relative motion of the arm. In particular, disc drives for data storage include a head that carries transducers to facilitate reading and/or writing of data on the disc. Also, glide testers are disc drive units that are used to examine data storage discs for imperfections in the disc surface.
Disc drives are used for storing information, typically as magnetically encoded data, and more recently as optically encoded data, on a disc surface. The disc spin at high rotational velocities such that the head flies above the disc surface on a cushion of air. The suspension arm is used for radially accessing different data tracks on the rotating discs.
Generally, all hard drive discs are tested before shipment. During a glide test, the glide head or slider flies over a disc surface generally at a predetermined clearance from the disc surface, known as the glide height or fly height. If contact occurs between the glide head and a disc defect or asperity, forces on the glide head create responses that can be measured with transducers.
When any type of transducer head is flying above a spinning disc surface, heads experience undesirable radial forces, circumferential forces and yaw torques. The effects of these forces are preferably reduced or eliminated while necessarily allowing for roll and pitch movement of the transducer head. While the transducer head is experiencing these forces, an electrical connection must be maintained between the transducers and the signal processing components of the disc drive. A flexible circuit or flex cable provides the electrical connection between the head and the remaining portions of the disc drive unit.
The electrical connections preferably do not significantly effect the performance characteristics of the suspension assembly. As storage densities on disc recording media become higher, the performance characteristics of all of the disc drive components become more strict and tolerances are reduced. Therefore, as storage densities increase, it becomes even more important to reduce the effects on performance due to a flexible circuit.